Petrology of the Hawaiian Islands; IV. The formation of aa and pahoehoe

Author:

Washington, Henry S.

Title:

Petrology of the Hawaiian Islands; IV. The formation of aa and pahoehoe

Periodical:

American Journal of Science, 5th series

Year:

1923

Volume:

6

Pages:

409-423

Subject:

Petrology Hawaii Island Geochemistry Crystalization

Summary:

Washington reviews previous ideas on the formation of aa and pahoehoe. He shows that the difference in state of oxidation of the iron, and other chemical differences between aa and pahoehoe, are insignificant. He believes pahoehoe to be generally less crystalline and poorer in gas than aa. Aa remains more fluid than pahoehoe, losing its gas more slowly, both temperature and gas content being partially maintained by crystallization. Aa cools more slowly than pahoehoe, and therefore crystallizes more completely. [Washington's ideas seem contradictory because they are based on static notions, i.e., that aa and pahoehoe have characteristic temperatures, gas contents, and cooling histories. Modern study has emphasized the dynamic characteristics of aa and pahoehoe, such as changing ratios of stress to strain, in formulating hypotheses to explain their origin.]

Label:

Geology

Date:

1923

Collection:

Periodicals